Epidemiological studies in human medicine have revealed an increase in the lifetime risk of cancer with the increasing use of medical imaging and, more specifically, increasing ionizing radiation. Medical imaging modalities that involve ionizing radiation include CT, nuclear medicine, conventional radiography, and fluoroscopy. The amount of ionizing radiation that a patient or radiation worker is exposed to is expressed by the term effective dose, which is the sum of the tissue-weighted equivalent doses for all tissues and organs across the whole body. The equivalent dose is calculated from the amount of radiation absorbed by a specific tissue or organ and the biologic effectiveness of that radiation as determined by the radiation type and energy. To calculate the effective dose, the equivalent dose for each tissue or organ is first multiplied by a tissue-weighting factor that accounts for the sensitivity of that tissue to an ionizing radiation–induced genetic defect or cancer (ie, stochastic effects). Values for each organ and tissue are then summed to provide a whole-body estimate of stochastic effects.1
The annual effective dose of ionizing radiation attributable to medical exposure in people has risen from 0.53 mSv in 1980 to 3.0 mSv in 2006.2 Data regarding medical exposure suggest that CT accounts for approximately 49% and nuclear medicine accounts for approximately 26% of ionizing radiation due to medical imaging.3 Estimates based on data concerning Japanese survivors of the atomic bomb indicate that up to 2% of future cancers may be attributable to CT scan exposure.4 Other estimates indicate that the 4 million pediatric CT scans of the head, abdomen or pelvis, chest, or spine performed each year will result in the development of 4,870 cancers.5
Given the increasing use of CT and digital radiography in small animal veterinary practice,6–8 veterinarians may expect increases in the number of these procedures performed and the mean effective dose of ionizing radiation to which patients are exposed. Patients of small animal veterinary referral institutions, where there is greater access to CT, fluoroscopy, and nuclear medicine, could be expected to have higher rates of exposure to ionizing radiation than patients of primary care institutions. Awareness of the effective dose ranges for various medical imaging procedures and the optimal safe use of diagnostic imaging equipment can impact the standard of patient care as well as the safety of personnel working around ionizing radiation sources. Information regarding the effective dose to which veterinary patients are exposed is limited; however, the effective dose associated with CT of the brain in dogs has been estimated to be similar to that in a 10-year-old child.a
As in human medicine, several studies in small animal medicine have revealed associations between exposure to ionizing radiation and subsequent development of cancer. For example, the incidence (4.24/1,000) of malignant tumors within the first 2 years of life for Beagles subjected to whole-body γ radiation at various points during the perinatal period was almost 3 times the spontaneous rate in the general canine population in 1 study.9 Furthermore, the incidence of fatal cancer in the irradiated Beagles was > 10 times the expected rate for the general canine population.9 In other studies,10,11 dogs exposed to β-emitting radionuclides had an increased risk of lung tumors that was dose dependent. Adverse effects of ionizing radiation other than cancer in both humans and small animals include erythema and alopecia, premolar hypodontia, low brain weight, immature dysplastic glomeruli, ocular sequelae (severe keratitis, conjunctivitis, keratoconjunctivitis sicca, cataracts, and uveitis), and an increase in the incidence of diabetes mellitus.12–14
In human medicine, studies15,16 have shown that physicians, radiologists, and residents are poorly aware of radiation safety matters. We suspected that the situation would be similar in veterinary medicine and that opportunities would exist to improve the education and training of specialist veterinary practitioners. The purpose of the study reported here was to evaluate the knowledge of various veterinary specialists regarding patient effective dose, the risk of ionizing radiation to veterinary patients, and occupational radiation safety matters and to determine the availability of radiation safety training.
Materials and Methods
Participants
The study protocol was reviewed and approved by the Tufts Health Sciences Campus Institutional Review Board. The survey was designed so that respondents were required to answer an informed consent question prior to proceeding. The target population was small animal veterinary internal medicine clinicians, ECC clinicians, and radiologists. Internal medicine and ECC clinicians were chosen from among the various veterinary specialties because their departments historically requested the largest number of medical imaging services across a wide array of imaging modalities available at the Foster Hospital for Small Animals at Tufts University.
Survey
The survey was designed and administered with the aid of a web-based survey tool.b In total, 27 questions were included (Supplementary Appendix S1, available at avmajournals.avma.org/doi/suppl/10.2460/javma.252.9.1133); the questions actually displayed to an individual respondent varied on the basis of the respondent's specialty (internal medicine, ECC, or radiology) and responses to prior questions. The survey questions were developed by the authors (SLG, JSS, and AFS), with refinements and guidance from the Tufts Office of Institutional Research and Evaluation (JAM and KJM). Survey functionality was tested (SLG, JSS, and JAM) prior to distribution via email invitation through the email lists of the ACVIM, ACVECC, and ACVR on June 22, 2015. The survey was open to responses until July 20, 2015 (29 days). Weekly reminders were sent during the survey period. Data collected through the survey tool were downloaded to and analyzed in a statistical software program.c
Estimated effective doses
Effective doses were estimated for 3 medical imaging procedures: 3-view thoracic radiography, 3-phase esophagography, and 3-phase abdominal CT. Three-view thoracic radiography was selected because this technique is commonly used at the Foster Hospital for Small Animals and was believed to represent a relatively low effective dose. Three-phase esophagography was selected as an example of a fluoroscopic procedure performed in veterinary medicine and, although uncommonly used, was believed to represent the moderate effective doses associated with fluoroscopy. Three-phase abdominal CT was selected because it was believed to represent a procedure used in veterinary medicine associated with a high effective dose.
A literature search revealed no studies providing effective dose estimates for veterinary patients exposed to survey radiography or fluoroscopy. Therefore, given the reporta that indicated the effective dose for CT of the brain in dogs is similar to that for a 10-year-old child, human data for children1 were used as estimates of the effective doses for 3-view thoracic radiography, 3-phase fluoroscopic esophagraphy (involving barium liquid, barium paste, and barium-soaked food), and 3-phase abdominal CT (precontrast, arterial, and delayed phases) in dogs. Although actual estimated effective doses for veterinary patients were expected to differ from these human estimates, the differences in order of magnitude for the 3 imaging techniques were considered appropriate for study purposes.
The effective dose for 3-view thoracic radiography was estimated as 3 times the effective dose associated with obtaining an anterior-posterior thoracic radiograph for a 10-year-old child (0.025 mSv × 3 = 0.075 mSv).1 The effective dose for 3-phase esophagography was estimated by combining the dose associated with a fluoroscopic barium swallow and barium meal for a 10-year-old child (0.760 mSv + 2.137 mSv = 2.897 mSv).1 For 3-phase abdominal CT, the effective dose was extrapolated from that for a 10-year-old child (5.8 mSv).1 Abdominal ultrasonography and MRI of the brain were selected as veterinary procedures that involve no ionizing radiation and are therefore associated with an effective dose of 0.0 mSv.
Statistical analysis
The χ2 test of independence was used to determine whether a difference existed in response rates among the ACVR, AVECC, and ACVIM email lists; academic institutions were more likely to have active radiation safety training programs than private practice; radiologists were more accurate in estimating effective doses than internal medicine and ECC clinicians; a difference existed between internal medicine clinicians and ECC clinicians in the ability to accurately estimate effective dose; a relationship existed between the number of years in practice and the ability to correctly estimate the effective dose; and radiologists were more likely than internal medicine and ECC clinicians to believe that there is a potential increased lifetime risk of fatal cancer resulting from ionizing radiation used during CT. For analysis comparing internal medicine and ECC clinicians with radiologists, internal medicine and ECC clinicians were grouped together. Survey responses of “Don't know” were treated as “No” in the analysis given that both responses were undesirable. Because each question was analyzed only once, no single analysis impacted the type I error rate or degrees of freedom of another analysis. Values of P < 0.05 were considered significant.
Results
Respondents
Survey responses were received from 384 invited participants. Of these, 28 (7.3%) were excluded because they were not currently employed at an academic institution or private practice. Employment status or field for excluded respondents included teleradiology or telemedicine (n = 11), retired (5), industry or corporate (4), semiretired or teleradiology (2), military or government (2), Veterinary Information Network (1), humane society (1), and academic and teleradiology (1). Of the remaining 356 respondents who reported being employed at a private practice (132 [37.1%]) or academic institution (224 [62.9%]), 324 (91.0%) completed the entire survey; however, all responses were retained provided respondents answered at least 1 question other than this initial question.
Primary area of practice for the 356 included respondents was radiology (n = 164 [46.1%]), ECC (108 [30.3%]), internal medicine (81 [22.8%]), and not reported (3 [0.8%]). Numbers of email-list members at the time of the study were 450 for ACVR, 452 for ACVECC, and 1,393 for ACVIM, representing response rates of 36.4%, 23.9%, and 5.8%, respectively, and an overall response rate of 16.7%. American College of Veterinary Radiology members were significantly (P < 0.001) more likely to respond than ACVECC or ACVIM members, and ACVECC members were significantly (P < 0.001) more likely to respond than were ACVIM members.
Overall, 3.9% (n = 14) of respondents had been practicing in their specialty for < 1 year, 26.4% (94) for 1 to 5 years, 22.5% (80) for 6 to 10 years, 17.1% (61) for 11 to 15 years, 11.8% (42) for 16 to 20 years, and 18.3% (65) for > 20 years. Location of previous residency was reported by 352 respondents, of which 84.7% (n = 298) indicated an academic institution, 13.6% (48) indicated private practice, and 1.7% (6) indicated other.
Medical imaging
In response to a question regarding types of imaging modalities available at their institution, 98.6% (n = 348) of 353 respondents indicated radiography, 98.0% (346) indicated ultrasonography, 88.4% (312) indicated CT, 70.0% (247) indicated MRI, 66.3% (234) indicated fluoroscopy, and 37.1% (131) indicated nuclear medicine or positron emission tomography. Overall, 19.1% (n = 68) of 356 respondents had 1 radiologist in their institution, 19.4% (69) had 2 radiologists, 14.0% (50) had 3 radiologists, 28.9% (103) had ≥ 4 radiologists, 17.4% (62) had no on-staff radiologist but had access to a traveling or online radiology service, and 1.1% (4) had none of these options.
Of 143 radiologists who provided answers, 46.9% (n = 67) indicated that technicians or students at their institution were instructed to obtain radiographs by being in the radiography room and providing manual patient restraint, 25.2% (36) by providing patient sedation (when possible) and physical restraints such as sandbags, and 28.0% (40) by both techniques equally.
Radiation safety training
Academic institutions were significantly (P = 0.001) more likely to provide mandatory radiation safety training for all medical personnel who work with ionizing radiation–emitting equipment than were private practices, but not for all hospital personnel (Table 1). Respondents from academic institutions were also significantly (P < 0.001) more likely to have received radiation safety training at their current institution than respondents from private practices. When asked about the frequency of radiation safety training, the most common response for respondents from academic institutions was annual training (33.6%), whereas the most common response for respondents from private practices was training only once (34.3%).
Proportion (%) of veterinary specialists in internal medicine, ECC, and radiology employed at an academic institution or private practice with various responses to survey questions regarding radiation safety training.
| Paraphrased question and response | Academic institution | Private practice |
|---|---|---|
| Is radiation safety training mandatory for all medical personnel at your institution (regardless of whether they work with ionizing radiation–emitting equipment)? | ||
| Yes | 72/110 (55.4) | |
| No or don't know | 58/110 (44.6) | 110/217 (50.7) |
| Is radiation safety training mandatory for all medical personnel who work with ionizing radiation–emitting equipment at your institution? (if no or don't know in response to previous question)* | ||
| Yes | 38/58 (65.5) | 33/110 (30.0) |
| No or don't know | 20/58 (34.5) | 77/110 (70.0) |
| Are radiation safety practices discussed in your employee or practice manual? | ||
| Yes | 73/123 (59.3) | 138/210 (65.7) |
| No or don't know | 50/123 (40.7) | 72/210 (34.3) |
| What is the frequency of radiation safety training at your institution? | ||
| 1 time only | 27/107 (25.2) | 47/137 (34.3) |
| Once yearly | 36/107 (33.6) | 44/137 (32.1) |
| More frequently than yearly | 5/107 (4.7) | 9/137 (6.6) |
| Less frequently than yearly | 15/107 (14.0) | 14/137 (10.2) |
| Don't know | 24/107 (22.4) | 23/137 (16.8) |
| Have you have received radiation safety training at your current institution?* | ||
| Yes | 85/106 (80.2) | 77/136 (56.6) |
| No | 21/106 (19.8) | 59/136 (43.4) |
| Does your institution have an assigned radiation safety officer?* | ||
| Yes | 98/125 (78.4) | 119/212 (56.6) |
| No or don't know | 27/125 (21.6) | 93/212 (43.9) |
| Are personnel who work with ionizing radiation–emitting equipment at your institution assigned individual dosimetry badges? | ||
| Yes | 124/126 (98.4) | 202/207 (97.6) |
| No or don't know | 2/126 (1.6) | 5/207 (2.4) |
Distributions of responses differ significantly (P < 0.05) between groups.
See Supplementary Appendix S1 for actual questions and question logic.
Of 244 respondents from institutions where radiation safety training was provided (multiple choices allowed), 63.5% (n = 155) indicated that this training was provided in person by a practice employee, 37.3% (91) indicated it was provided online, 29.5% (72) indicated it was self-taught through reading materials or an employee manual, 14.8% (36) indicated it was provided in person by an external source, 4.9% (12) indicated that training was offered through other options, and 9.0% (22) indicated no knowledge of how training was offered. Overall, 88.4% (n = 213) of 241 respondents indicated that during training, discussion took place on minimizing the dose of ionizing radiation to which personnel are exposed.
Most respondents who reported radiation safety training at their institution (218/239 [91.2%]) indicated that time, distance, and shielding were discussed during training, whereas 20 (8.4%) reported that they did not know. Only 1 participant indicated that these topics were not discussed during training. One hundred eleven of 241 (46.1%) respondents indicated that training included discussion on limiting the effective dose of ionizing radiation to patients. Of 238 respondents who reported that radiation safety training was provided at their institution, 158 (66.4%) indicated that they knew what the abbreviation ALARA stood for. Of those 158, 148 (93.7%) correctly defined that abbreviation.
Radiation safety practices
Academic institutions were significantly (P < 0.001) more likely to have an assigned radiation safety officer than private practices (Table 1). Both private practices and academic institutions had high percentages (96.2% [n = 202] and 98.4% [124], respectively) of respondents who indicated that personnel who worked with ionizing radiation–emitting equipment were assigned individual dosimetry badges.
Respondents were asked 2 questions regarding their institution's typical responses to personnel who were found to have violated radiation safety practices, such as obtaining radiographs with an ungloved hand in line of the primary x-ray beam or without a protective lead apron and thyroid gland shield. In response to personnel with first offenses and multiple offenses, respectively, 65.7% (n = 218) and 50.6% (168) of respondents indicated that the individual would be verbally warned by a radiologist or administrator regarding the breach in safety protocols, 59.9% (199) and 36.7% (122) indicated that the individual would be educated in radiation safety practices, 29.5% (98) and 22.9% (76) indicated that the finding and potential hazard would be documented in the radiographic report, 7.8% (26) and 43.1% (143) indicated that more severe disciplinary action would be taken, 7.2% (24) and 3.6% (12) indicated that no action would be taken, and 8.4% (28) and 20.5% (68) indicated that they did not know.
Estimation of effective dose
In general, neither internal medicine and ECC clinicians nor radiologists were accurate in estimating effective dose, although radiologists were significantly (P < 0.001) more likely to do so for 3-view thoracic radiography (Table 2). Radiologists were also significantly (P < 0.001) more likely to know that ultrasonography and MRI do not involve the use of ionizing radiation. No significant differences were identified between proportions of radiologists and proportions of internal medicine and ECC clinicians regarding the correct effective doses associated with 3-phase esophagography and 3-phase abdominal CT, nor were any differences in proportions identified between internal medicine clinicians and ECC clinicians regarding correct effective doses associated with any medical imaging procedure featured in the survey. Years in practice had no association with the ability to correctly estimate the effective dose of any imaging procedure.
Survey response distributions for estimates by veterinary radiologists and internal medicine and ECC clinicians of the effective dose of ionizing radiation associated with various medical imaging procedures.
| Estimated effective dose (mSv) per procedure | Radiologists | Internal medicine and ECC clinicians |
|---|---|---|
| 3-view thoracic radiography | ||
| 0 | 0 | 3/155 (1.9) |
| 0.1–0.5 | 91/143 (63.6) | 61/155 (39.4) |
| 0.5–1.0 | 22/143 (15.4) | 33/155 (21.3) |
| 1–5 | 13/143 (9.1) | 28/155 (18.1) |
| 5–10 | 10/143 (7.0) | 20/155 (12.9) |
| 10–50 | 5/143 (3.5) | 7/155 (4.5) |
| 50–100 | 2/143 (1.4) | 3/155 (1.9) |
| > 100 | 0 | 0 |
| 3-phase esophagography | ||
| 0 | 0 | 3/153 (2.0) |
| 0.1–0.5 | 12/143 (8.4) | 10/153 (6.5) |
| 0.5–1.0 | 44/143 (30.8) | 43/153 (28.1) |
| 1–5 | 42/143 (29.4) | 31/153 (20.3) |
| 5–10 | 20/143 (14.0) | 37/153 (24.2) |
| 10–50 | 12/143 (8.4) | 19/153 (12.4) |
| 50–100 | 9/143 (6.3) | 7/153 (4.6) |
| > 100 | 4/143 (2.8) | 3/153 (2.0) |
| 3-phase abdominal CT | ||
| 0 | 0 | 1/154 (0.6) |
| 0.1–0.5 | 3/143 (2.1) | 2/154 (1.3) |
| 0.5–1.0 | 11/143 (7.7) | 19/154 (12.3) |
| 1–5 | 24/143 (16.8) | 33/154 (21.4) |
| 5–10 | 38/143 (25.6) | 29/154 (18.8) |
| 10–50 | 31/143 (21.7) | 33/154 (21.4) |
| 50–100 | 16/143 (11.2) | 20/154 (13.0) |
| > 100 | 20/143 (14.0) | 17/154 (11.0) |
| MRI of the brain | ||
| 0 | 144/145 (99.3) | 119/155 (76.8) |
| 0.1–0.5 | 0 | 9/155 (5.8) |
| 0.5–1.0 | 1/145 (0.7) | 7/155 (4.5) |
| 1–5 | 0 | 1/155 (0.6) |
| 5–10 | 0 | 4/155 (2.6) |
| 10–50 | 0 | 4/155 (2.6) |
| 50–100 | 0 | 6/155 (3.9) |
| > 100 | 0 | 5/155 (3.2) |
| Abdominal ultrasonography | ||
| 0 | 144/145 (99.3) | 130/158 (82.3) |
| 0.1–0.5 | 1/145 (0.7) | 21/158 (13.3) |
| 0.5–1.0 | 0 | 6/158 (3.8) |
| 1–5 | 0 | 1/158 (0.6) |
| 5–10 | 0 | 0 |
| 10–50 | 0 | 0 |
| 50–100 | 0 | 0 |
| > 100 | 0 | 0 |
Data reported are proportion (%) of group. Correct responses appear in bold font.
See Table 1 for remainder of key.
Many radiologists (92/153 [60.1%]) and internal medicine or ECC clinicians (92/179 [51.4%]) did not believe that the high effective doses of ionizing radiation used in veterinary CT carry an increased risk of potentially fatal cancer. In response to a hypothetical scenario of a study that identified the potential for a 0.1% increased lifetime risk of fatal cancer resulting from performance of a high effective dose procedure on a young animal (eg, CT angiography to evaluate for a portosystemic shunt), internal medicine and ECC clinicians (n = 76 [42.5%]) were significantly (P < 0.001) more likely to choose an alternative modality of similar diagnostic value than were radiologists (37 [24.2%]). Seventy eight of 180 (43.3%) internal medicine and ECC clinicians indicated that they had had a client ask about the risk of radiation associated with medical imaging procedures, whereas only 2 (1.1%) indicated that they routinely warned clients that there may be an increased risk of cancer from such procedures. Most radiologists (113 [73.9%]) reported not warning clinicians that the use of ionizing radiation in medical imaging procedures may carry an increased risk of cancer.
Discussion
Knowledge of the veterinary specialists surveyed in the study reported here appeared to be limited regarding effective doses of ionizing radiation associated with medical imaging procedures and, more importantly, the potential for adverse effects such as cancer from these imaging procedures. Although radiologists were significantly more likely to be accurate in identifying the correct effective dose estimate for 3-view thoracic radiography, radiologists and internal medicine and ECC clinicians were equally unlikely to correctly identify the effective doses associated with 3-phase abdominal CT and 3-phase esophagography. These findings raised some concern given that specialist veterinary radiologists receive training in radiation safety and radiation biology and may be expected to run and support radiation protection programs within their institutions. The findings were similar to those reported for human health-care centers, where low proportions of diagnostic radiology residents (48% correct responses) and obstetrics-gynecology and pediatric medicine residents and faculty as well as radiology faculty (15% to 22% correct responses) were able to correctly identify the effective dose of ionizing radiation associated with abdominal CT.16
Effective doses of ionizing radiation associated with CT scans of people have been estimated by means of a voxel-based Monte Carlo simulation technique and calculation of the radiation-absorbed dose from the images of phantoms and patients.17 A studya in which similar techniques were applied to dogs to estimate the effective dose associated with CT of the brain included no assessment of other organ systems. It is important to consider that the effective dose to which any individual patient is exposed during CT examination will vary on the basis of patient characteristics and the area imaged as well as scan parameters, such as tube current and voltage; scanning modes, length, and collimation; table speed and pitch; gantry rotation time; and shielding. Additional studies are needed to validate the use of Monte Carlo techniques for estimating effective doses for other organs systems in veterinary patients.
In the study reported here, most veterinary internal medicine and ECC clinicians and radiologists did not believe that the estimated effective doses inherent to CT imaging procedures carry an increased risk of cancer in veterinary patients. Given that such an increased risk is well documented in the human literature,2–5 this finding was surprising. Respondents may have believed that canine and feline patients do not live as long as their human counterparts and, therefore, do not live long enough to develop cancer secondary to ionizing radiation. However, the authors believe that the increased risk of cancer identified for human patients is also possible for veterinary patients. The reported baseline lifetime risk of fatal cancer in people is 25%,16 which is an estimate that excludes consideration of individual factors, such as lifestyle (eg, smoking, diet, and exercise), family history (ie, genetics), and radiation exposure. For every 100 mSv of ionizing radiation exposure for this population, lifetime cancer mortality risk increases by 0.5 %.16 Interestingly, when responding to the hypothetical scenario involving a 0.1% risk of cancer development in young dogs undergoing abdominal CT, most veterinary radiologists and internal medicine and ECC clinicians in the present study indicated that this information would not change their use of the procedure. We propose that this response reflected the perception that in many instances, the diagnostic usefulness of the preferred imaging test greatly outweighs the risk of induced cancer.
The present study revealed some interesting findings regarding radiation safety in veterinary specialty centers. Radiation safety training appeared to be more robust in some academic institutions than in private practices. However, ongoing training was reportedly infrequent in both practice settings. In addition, a large proportion of veterinary specialists were unaware of a radiation safety officer at their institution, even though almost all states require someone to act in this capacity at each practice. We performed a search of the websites for all state health departments, which revealed that 28 states require the name of a person responsible for radiation protection or radiation safety officer on the practice radiography equipment license application and 21 states require a named person on the equipment license. These named people are then required according to the state radiation safety guidelines to either delegate or fulfill the duties typically assumed by a radiation safety officer. The respondents' lack of knowledge regarding this person's identity at their own institution may have suggested that the person's profile and contributions in this role may not have been adequate or adequately communicated. It is important that at all institutions, particularly private practices, efforts be made to raise the visibility of the assigned radiation safety officer and that this person develop a strong and informative radiation safety training program to ensure personnel and patient safety as well as legal compliance.
Although the present study was not designed to fully evaluate the effectiveness of the radiation safety training that the respondents received, a few conclusions could be drawn from the study data. A large proportion (91.2%) of respondents who had received radiation safety training indicated that this training involved discussion of time, distance, and shielding, which is an encouraging finding given that these factors are important to minimize personnel exposure. However, only 62.9% of the participants who responded from institutions where training was in place correctly defined the abbreviation ALARA.
Although correct memorization of an abbreviation's definition does not necessarily reflect a veterinary specialist's approach to the use of ionizing radiation, ALARA represents a fundamental principle in radiation safety and training. This principle aims to decrease the amount and duration of exposure to ionizing radiation when clinically feasible, thus limiting the effective doses to which personnel and patients are exposed. Application of the ALARA principle includes understanding the advantages and disadvantages of all imaging modalities, particularly ultrasonography and MRI given that these modalities involve no ionizing radiation. Nearly half of the radiologists from academic institutions in the study reported here indicated that students or technicians were primarily taught to obtain radiographs in the radiography room using manual restraint. Although not always feasible, performance of radiography with personnel outside the radiography room is a practice in best accordance with the ALARA principle. A high proportion (88.4%) of the respondents who had received radiation safety training indicated that the training included discussion of limiting personnel radiation exposure, whereas less than half indicated that the training included discussion of limiting patient effective dose.
In human medicine, the radiation safety culture has taken a major shift toward the discussion of limiting patient effective dose as well as the traditional concerns of occupational safety. The Image Gently campaign started by the Alliance for Radiation Safety in Pediatric Imaging aims to improve patient protection from ionizing radiation by providing health-care networks with informational materials describing the risks and benefits of the ionizing radiation–emitting imaging modalities.18 Although research is lacking in veterinary medicine to confirm an association between medical imaging–associated ionizing radiation and cancer, a similar initiative could result in greater consideration of patient effective dose and also benefit personnel who perform such imaging. The degree of knowledge about radiation safety identified in the surveyed veterinary specialists was similar to that held by 412 surveyed human health-care workers, who primarily consisted of radiologic technologists, 79.1% of whom were able to correctly define ALARA.19 In that study,19 a high proportion of respondents (99.3%) were also able to identify time, distance, and shielding as the 3 methods of reducing radiation exposure. Additional research into the methods, frequency, and content of radiation safety training is needed within the broader veterinary community to determine optimal approaches to promoting radiation safety.
Limitations of the study reported here included a low response rate and the inclusion of respondents from specialty hospitals that may have had dedicated radiology departments and a larger administrative structure than primary veterinary practices. Indeed, the findings could be expected to be different if respondents from primary veterinary practices were included. Additionally, to preserve anonymity of the respondents, no information was requested regarding the identity of their place of employment, so it remains unknown whether the respondents included multiple individuals from the same institution, and a lack of control for this variable may have biased the results. Another limitation was the lack of known effective dose estimates for veterinary patients. Inclusion of estimate ranges as response options in the survey may have affected the ability of respondents to intuitively choose the correct effective dose estimates. Lastly, veterinary specialists who routinely use ionizing radiation–emitting equipment may have been more likely to respond to the survey than those who do not.
Overall, most radiologists, internal medicine clinicians, and ECC clinicians who responded to the survey had a poor understanding of the amount of ionizing radiation associated with medical imaging and believed there is no risk of fatal cancer development to patients undergoing such procedures. Radiation safety training, although more common in academia, was not universally available, and knowledge of effective doses and radiation safety practices reflected this. Establishment of effective dose estimates associated with the various medical imaging procedures in veterinary medicine could lead to the development of risk projection models for estimating whether veterinary patients undergoing such procedures are at increased risk of developing fatal cancer, as has been reported for people. Research in this area could also lead to the development of more in-depth approaches to radiation safety training and strategies for reducing radiation exposure from medical imaging procedures.
Acknowledgments
Supported in part by the Willy Hale Research Fund. The authors thank Dr. Elizabeth Rozanski for contributing to study design and data collection.
ABBREVIATIONS
| ACVECC | American College of Veterinary Emergency and Critical Care |
| ACVIM | American College of Veterinary Internal Medicine |
| ACVR | American College of Veterinary Radiology |
| ALARA | As low as reasonably achievable |
| ECC | Emergency and critical care |
| mSv | Millisievert |
Footnotes
Hall C. Characterizing canine dose from external beam irradiation. MS thesis, Department of Environmental and Radiological Health Sciences, Colorado State University, Fort Collins, Colo, 2011.
Qualtrics software, versions 5–8/2015, Qualtrics, Provo, Utah.
SPSS, version 23, IBM Corp, Armonk, NY.
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